The present invention relates to a video printer for printing video information on a transfer print medium.
There has heretofore been known a thermal transfer printer which is supplied with an image signal from an image data input device such as a camera, a video tape recorder, or the like, and heats and presses a thermal transfer ribbon against a print sheet with a thermal head to print an image on the print sheet. The thermal transfer ribbon and the print sheet are referred to as a print medium. Such print mediums include a non-transfer print medium for printing an image on a print sheet and a transfer print medium for printing an image on a print sheet and then transferring the printed image from the print sheet to another object.
A conventional process of printing an image on a transfer print medium with a thermal transfer printer will be described below. The transfer print medium has a print sheet which is composed of a base sheet and a transfer sheet applied to the base sheet. The transfer sheet doubles as a sheet on which an image is to be printed. After an image has been printed on the transfer sheet of the print sheet, only the transfer sheet with the printed image is applied from the base sheet to an object such as a cup, a piece of cloth, or the like by way of thermal transfer. The image printed on the transfer sheet now appears as if printed on the object itself. The image transferred to the object is a horizontal reversal of the image which is printed on the transfer sheet.
Even if the object has a curved surface such as a side wall of a cup, an image can easily be transferred to the curved surface by printing the image on a print sheet and then applying only the transfer sheet to the object by way of thermal transfer.
The thermal transfer printer is usually designed to print images on non-transfer print mediums. Therefore, the thermal transfer printer has conventionally effected a single gamma correction process so that an image printed on the print sheet of a non-transfer print medium can clearly be seen, or stated otherwise, has a proper image density. However, if an image is printed on a transfer print medium by the thermal transfer printer and then transferred to an object, since the image has not been gamma-corrected based on the transfer characteristics of the transfer print medium, the quality of the transferred image depends upon the characteristics of the transfer print medium itself.
Specifically, inasmuch as the gamma correction carried out on the conventional thermal transfer printer has single characteristics for printing images on non-transfer print mediums, the same gamma correction is effected by the thermal transfer printer on images printed on transfer print mediums whose print sheets have transfer sheets and on images printed on non-transfer print mediums whose print sheets have no transfer sheets. Accordingly, images formed on transfer print mediums often tend to have improper densities.
Image transfer from transfer print mediums to objects is also disadvantageous in that an image transferred from a transfer print medium to an object is a horizontal reversal, i.e., a mirror-image reversal, of the original image.